The mean type Ia Supernova spectrum over the past nine gigayears
Abstract
We examine the possibility of evolution with redshift in the mean rest-frame ultraviolet (UV; λ ≾ 4500 Å) spectrum of Type Ia Supernovae (SNe Ia) sampling the redshift range 0 < z < 1.3. We find new evidence for a decrease with redshift in the strength of intermediate-mass element (IME) features, particularly Si II and to a lesser extent Ca II "H&K" and Mg II blends, indicating lower IME abundances in the higher redshift SNe. A larger fraction of luminous, wider light-curve width (higher "stretch") SNe Ia are expected at higher redshift than locally, so we compare our observed spectral evolution with that predicted by a redshift-evolving stretch distribution coupled with a stretch-dependent SN Ia spectrum. We show that the sense of the spectral evolution can be reproduced by this simple model, though the highest redshift events seem additionally deficient in Si and Ca. We also examine the mean SN Ia UV-optical colors as a function of redshift, thought to be sensitive to variations in progenitor composition. We find that the expected stretch variations are sufficient to explain the differences, although improved data at z ~ 0 will enable more precise tests. Thus, to the extent possible with the available data sets, our results support the continued use of SNe Ia as standardized candles.
Additional Information
© 2009 The American Astronomical Society. Received 2008 October 8; accepted 2009 January 15; published 2009 February 18. M.S. and R.S.E. acknowledge support from the Royal Society. P.E.N. acknowledges support from the US Department of Energy Scientific Discovery through Advanced Computing program under contract DE-FG02-06ER06-04. A.G. acknowledges support by the Benoziyo Center for Astrophysics, a research grant from Peter and Patricia Gruber Awards, and the William Z. and Eda Bess Novick New Scientists Fund at the Weizmann Institute.Attached Files
Published - Sullivan2009p1047Astrophys_J_Lett.pdf
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Additional details
- Eprint ID
- 14054
- Resolver ID
- CaltechAUTHORS:20090423-093939534
- Royal Society
- Department of Energy (DOE)
- DE-FG02-06ER06-04
- Benoziyo Center for Astrophysics
- Peter and Patricia Gruber Foundation
- William Z. and Eda Bess Novick New Scientists Fund at the Weizmann Institute
- Created
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2009-04-23Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field